Hydra

Hydras, sometimes called "bugs" in in-game documents, are arthopods mutated by HO-213 exposure. The original organism they were is unknown; it is possible they were simple cockroaches prior to the infection converting them to their current, trilobyte-like forms, but little is known. In their current state, they serve as vanguard organisms for the HO-213 infection, spreading it to other organisms to push the infection onwards. Gifted with an extremely rapid breeding cycle, Hydras can proliferate extremely fast, and often attack prey in large groups as a result, so while each Hydra is rather weak individually, in groups they constitute a significant threat. While their body weight has increased to the point where they can no longer fly, their wings do allow them to hover short distances and their tails let them make impressive leaps.

Combat Analysis
Hydras are the weakest enemy in Extermination, and one of the most common. They're easy to take out - one single heavy swing from the knife or a bullet or two from the SPR4 is often sufficient - but they're so common that it's extremely easy for a player to get tagged by a stray attack if they aren't careful, and all of a Hydra's attacks boost infection.

The Hydra's main method of attacking is to spit a glob of infectious fluid at you. It has longer range than one might expect, and a low, arcing trajectory, boosting infection by about 10% with each hit. Its secondary attack is to leap into the air and fly at the player, latching on if they hit. If the player doesn't throw them off quickly (by jamming on the buttons), the Hydra will self-destruct, covering their victim in viral juices and boosting their infection considerably (25% or more). Roger Grigman succumbed to this attack after about five Hydras did it to him at once.

If possible, engage and destroy Hydras at long range or individually.

Second-Stage Mutation
Exposure to Water mutates the Hydra into its second-stage mutation. It nearly doubles in size, gaining a mottled brown carapace, and it becomes more aggressive. Second-Stage Hydras do much more damage with their infectious attacks, and take roughly twice as much abuse to bring down. Be extra careful around these modified plague-spreaders.